Luminance and chrominance signal separator using correlation detection

Abstract

A device that separates a luminance signal and a chrominance signal from an input composite color television signal, suppressing cross color interference and keeping a good color transient characteristic, by selecting characteristics of the color bandpass filters according to a vertical correlation value after obtaining a chrominance signal at an adaptive type comb filters. The apparatus includes a cascade connection of a plurality of delay devices each one of which delays one horizontal period; chrominance correlation detecting circuits for obtaining correlation of a chrominance signal between a reference signal and a signal at the vertical vicinity of the point of the reference signal on the screen, where an output signal of the central delay device is regarded as a reference signal; luminance correlation detecting circuits for obtaining correlation of a luminance signal between the reference signal and a signal at the vertical vicinity of the point of the reference signal on the screen; a correlation judging circuit for judging if there is correlation from the correlation of the chrominance signals and the correlation of the luminance signals; comb filters for separating a chrominance signal from the composite color television signal; and a selector for selecting an output of the comb filters according to the judgment of the correlation.

What is claimed: 
     
       1. A luminance and chrominance signal separating apparatus comprising: a cascade connection of at least four delay means, where each delay means delays a composite color television signal by a horizontal period and a signal at a junction point of said cascade connected delay means is regarded as a reference signal;   at least two chrominance correlation detecting means for calculating chrominance correlation values of a chrominance signal between said reference signal and signals at the vertical vicinity of said reference signal on the screen, wherein each of the signals in the vertical vicinity of said reference signal is separated from the reference signal by a delay greater than one horizontal period;   at least two luminance correlation detecting means for calculating luminance correlation values of a luminance signal between said reference signal and signals vertically adjacent to said reference signal on the screen;   a correlation judging means for judging if there is correlation or not from the chrominance correlation values and luminance correlation values;   a plurality of comb filters for separating a chrominance signal from said composite color television signal;   selecting means for selecting the outputs of said comb filters according to the correlation judged at said correlation judging means;   frequency band limiting means for limiting the output signal of said selecting means and outputting a chrominance signal; and   subtracting means for subtracting the output signal of said selecting means from said reference signal and outputting a luminance signal.   
     
     
       2. A luminance and chrominance signal separating apparatus comprising: a cascade connection of at least four delay means, where each delay means delays a composite color television signal by a horizontal period and a signal at the central junction point of said cascade connected delay means is regarded as a reference signal, if the number of said delay means is even, and a signal at the junction point just ahead of or just behind the central delay means of said cascade connected delay means is regarded as a reference signal, if the number of said delay means is odd;   at least two chrominance correlation detecting means for calculating chrominance correlation values of a chrominance signal between said reference signal and signals at the vertical vicinity of said reference signal on the screen, wherein each of the signals in the vertical vicinity of said reference signal is separated from the reference signal by a delay greater than one horizontal period;   at least two luminance correlation detecting means for calculating luminance correlation values of a luminance signal between said reference signal and signals vertically adjacent to said reference signal on the screen;   a correlation judging means for judging if there is correlation or not from the chrominance correlation values and luminance correlation values;   a plurality of comb filters for separating a chrominance signal from said composite color television signal;   selecting means for selecting the outputs of said comb filters according to the correlation judged at said correlation judging means;   frequency band limiting means for limiting the output signal of said selecting means and outputting a chrominance signal; and   subtracting means for subtracting the output signal of said selecting means from said reference signal and outputting a luminance signal.